A Yad Vashem testimonial says that he was born in Sohrau in 1875, was married to Lisbeth, and that he died in Berlin, where he owned a factory.

His full date of birth is given by both Gmina Wyznania Mojżeszowego w Żorach 1511-1940 by Jan Delowicz and by his marriage certificate; the latter names his parents.

Oskar and Elizabeth are listed in the 1939 census of Berlin at Elsaesser Strasse 8, along with:
- Hildegard Apt born 05.07.1917,
- Ilse Bielschowsky geb. Apt born 20/04/1909
- Inge Apt-Bielschowsky born 01.03.1935,
- Petri Apt-Bielschowsky born 07.05.1937,
- Peter Bielschowsky born 07.05.1937.

I suspect that Peter and Petri are the same person; they could, however, be twins although I have found no records for Petri.

His gravestone in Berlin Weissensee cemetery, plot F1, which bears the same date of birth, gives a date of death in 1948, meaning that he survived the Nazi era and probably returned to Berlin after the war. The gravestone lists four people who perished in Auschwitz concentration camp: Ilse, Wilhelm, [Hans?] and Peter; it does not give their relationships to Oscar.